Fix problem when moving fullscreen window to scratchpad

Patch status: superseded

Patch by haptix@web.de

Long description:

When moving a fullscreen window to scratchpad with 'move scratchpad', the
focused window would stay fullscreen.
Also, when having a container in fullscreen mode and then focusing a child of
this container and moving it to scratchpad, it would enable fullscreen for
the child window.
This patch fixes both problems, so the scratchpad window is always floating.